Thermoplastic adhesives, otherwise known as “hot melt” adhesives, have been widely used in industry for adhering many types of products. Hot melt adhesive dispensing systems generally include one or more adhesive dispensing guns, heated hoses connected to the guns, and a dispensing unit for melting and supplying liquid adhesive to the guns through the heated hoses. The dispensing units of conventional hot melt adhesive systems can include a tank and heater, a pump, a manifold, and a controller. The manifold has an inlet connected to the tank and has multiple outlet ports for fluid connection to the heated hoses. Adhesive material is supplied to the tank in solid or semi-solid form, where it is melted and heated by the heater. A pump associated with the tank and manifold pumps liquid adhesive from the tank, through the manifold and heated hoses to the dispensing guns. The controller is generally located adjacent the tank and controls the power supplied to the heater and heated hoses to maintain the liquid adhesive at an appropriate viscosity and temperature according to the desired application.
The controller generally includes a main board which performs the power distribution functions of the dispensing system. In addition to the main board, the controller will generally include a CPU board and one or more power modules which are coupled with the main board and with the heated hoses. The controller is typically configured to be used with a predetermined number of guns and hoses (for example 2, 4, or 6 hoses). Users of adhesive dispensing systems often desire to upgrade the systems from, for example, two hose systems to four hose systems, or from four hose systems to six hose systems. However, the configuration of conventional controllers makes upgrading or other modification of the controller costly and very labor intensive. For example, the main board and power modules are typically housed in an enclosure and are coupled together by individual wiring harnesses. The power modules are in turn coupled to cord sets of the hoses using additional wiring harnesses. Accordingly, upgrading a conventional controller involves accessing the main board and power modules, uncoupling the associated wiring harnesses, removing the main board and power modules, installing a new main board and new power modules, and routing and connecting the new wiring harnesses. Furthermore, with some systems upgrading is not even possible.
In some applications, it may be desired to provide improved resistance to liquid infiltration into the controller. Such infiltration may occur, for example, by accidental spillage of liquid near the adhesive dispensing system, or by exposure to liquids during cleaning of the adhesive dispensing system or the immediate area surrounding the system. In these situations, it is desirable to prevent infiltration of liquids into the controller to prevent damage to electrical components contained therein.
The electrical components that make up the controller generate heat which must be dissipated to prevent overheating of the controller. Generally, heat sinks are added to conventional controllers to aid in the thermal management of the controller. However, fabricating or purchasing separate heat sinks and installing them on the controller represent additional costs which could be reduced or eliminated if a more efficient means of dissipating heat could be utilized.
There is thus a need for an improved controller which can be used with hot melt adhesive dispensing systems and which permits ready modification of the controller in the field for servicing or upgrading. There is also a need for a controller which provides improved resistance against liquid infiltration and simplifies the hardware required for thermal management.